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%
% MIT License
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% Copyright (c) 2016 Microsoft
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function Nid2 = decode_pss(du)
    rr = colfun(@(Nid2) xcorr(du, pss(Nid2)), 0:2);
    [~, k] = max(max(abs(rr)));
    Nid2 = k - 1;
    mag = sort(abs(rr(:,k)));
    if mag(end)/mag(end-1) < 3 % TODO: correct threshold?
        Nid2 = NaN; % signal no PSS received
    end
end
